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What is an electric charge?

Charge is the properties of matter. According to Benjamin franklin there are two types of charge, (1) Positive charge and (2) Negative charge.
Electric charge is a scalar quantity.
In SI System, the unit of Electric charge is Coulomb.
The dimensional formula of Electric charge is [ M0L0T1A1 ]

Coulomb's law


The force on a test charge Q due to a single point charge q is given by coulomb's law $$\vec{F} = \frac{1}{4\pi \epsilon_0 } \frac{Qq}{r^2} \hat{r}$$ Where r is the distance between Q and q and ε0 is the permitivity of the free space.



Electric field


The force per unit charge that would be exerted on a test charge is called electric field.



Electric flux


$$\Delta \phi = \vec{E}.\Delta S$$



Gauss's law


Electric flux ( φ ) through a closed surface (S) enclosing the total charge (q) is given by,


$$\phi = \frac{q}{\epsilon_0}$$


That is is the Gauss's law.



Electric dipole


If two equal and opposite charges +q and -q are separated by a distance 2d, then this arrangement is called electric dipole.

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How many fundamental and supplementary units in SI?

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Base unit

Physical quantity


Unit


Symbol




Mass


Kilogram


kg




Length


Metre


m





Time


Second


s





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Kelvin


K





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Ampere


A





Luminous intensity


Candela


cd





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Mole


mol




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Unit


Symbol




Plane angle


Radian


rad





Solid angle


Steradian


sr



Conversion factor
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1 centimetre = 10-2 metre
1 millimetre = 10-3metre
1 micrometre = 10-6metre
1 nanometre = 10-9 metre
1 angstrom= 10-10 metre
1 fermi = 10-15 metre
1 kilometre = 103 metre
1 austronomical unit = 1AU=1.496 × 1011 metre
1 light year = 1 ly = 9.461 ×1015metre
1 mile = 1.609 ×103 metre
1 yard = 0.9144 metre
1 inch = 0.0254 metre


Conversion of time

1 mili second= 10-3 second
1 micro second = 10-6 second
1 neno second = 10-9 second
1 hour = 60 minute = 3600 second
1 day = 24 hours =86400 second
1 year = 365 day = 3.156× 107 second
1 sec = 10-8second


Conversion of mass

1 gram = 10 -3 kg
1 quintal = 100 kg
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